1. Field of the Invention
The present invention relates to a collet chuck assembly for holding a tool or workpiece on a spindle of a turning machine.
2. Description of Related Art
Collets chucks are used in various machine tools such as lathes for clamping or gripping workpieces or tools. Collet heads include a plurality of circumferentially-spaced, workpiece-gripping segments and conical surfaces or cams, which, when the collet head is moved axially, interact with corresponding, opposing surfaces or cams on a mounting fixture or on the spindle. This interaction causes the workpiece-gripping segments of the collet head to contract or expand to grasp or release a workpiece or tool, depending on the direction of movement. Collet chucks have commonly been used in machine tools in place of other types of chucks. Collet chucks are typically more accurate and have a greater gripping characteristic than a typical jaw chuck, for example. Another advantage of collets is that they continue to grasp the workpiece or tool even at high rotational speeds when jaw chucks would have a tendency to loosen their grip due to centrifugal force.
One problem with such conventional collet chucks is that the required axial movement of the collet head axially moves the workpiece or tool as well. Consequently, slight variations in the diameter of the workpiece or tool could cause the collet to position the workpiece differently. When and where a collet will grasp a work piece depends on the difference in diameter between the open collet and the diameter of the workpiece. Precise workpiece diameter is therefore required if the workpiece is to be positioned precisely and consistently in machining operations such as facing, side finishing or cutting to precise lengths.
One conventional way of eliminating such axial movement is by using dead length collet chucks. In such chucks, the collet head is held in an axially-fixed position. A selectively axially-movable collet closing sleeve having a cam surface that engages the cams of the collet head is moved axially, instead of the collet head, to close and open the collet head. The closing sleeve is typically moved forwardly to close the collet head and rearwardly to open the collet head. Unfortunately, the collet head may have a tendency to occasionally stick to the collet closing sleeve when the sleeve is retracted to open the collet head. In such instances, the collet head tends to move axially-rearwardly with the collet closing sleeve. This results in the collet head not opening.
A conventional collet chuck typically extends over a substantial length in an axial direction of an associated machining tool (i.e. in a direction that extends along a rotational axis of the collet chuck). Consequently, the collet chuck intrudes into a machining envelope (work space) of the machining tool and limits the length of a workpiece or tool that can be held in the machining tool.
A conventional collet chuck typically has a small gripping diameter range (i.e., a small variation between the fully open and fully closed grip diameters). This small gripping range disadvantageously limits the chuck""s ability to grip stock (workpieces or tools) that has a diameter that varies from the intended gripping diameter. Accordingly, there is a need in the art for a collet chuck that can effectively grip variously-sized stock.
Another problem encountered by conventional collet assemblies is that collet seals that are disposed between the collet segments may not always be in complete contact with their adjoining collet segments. Consequently, debris can enter the collet chuck assembly between the segments.
One aspect of the present invention provides an improved collet head and collet chuck assembly.
Another aspect of the present invention provides a collet chuck assembly that simplifies collet head changing.
A further aspect of the present invention provides a collet chuck assembly with a double angle, outside diameter collet head.
A further aspect of the present invention provides a collet chuck assembly for holding a tool or work piece on a spindle of a turning machine. The collet chuck assembly has a mount having a front end and a rear end adapted to be connected to the spindle. The mount has an axial opening extending therethrough. An axially-extendable collet closing sleeve is disposed within the axial opening of the mount. The collet closing sleeve has a plurality of axially-spaced tapered inner surfaces. A collet head is disposed radially-inwardly from the collet closing sleeve. The collet head has a plurality of axially-spaced tapered outer surfaces that engage the tapered inner cam surfaces of the collet closing sleeve. The collet head has an inner order hole. Axial movement of the collet closing sleeve forces each of the outer surfaces of the collet head radially-inwardly, thereby reducing the inner diameter of the order hole.
A further aspect of the present invention provides a collet head having a plurality of circumferentially-spaced segments, each segment of which defines a portion of each of a plurality of axially-spaced circumferential cam surfaces. Each segment has surface portions disposed adjacent to corresponding surface portions of adjacent segments. The collet head also has resilient flat collet seals disposed between the adjacent surface portions.
A further aspect of the present invention provides a collet chuck assembly for holding a tool or work piece on a spindle of a turning machine. The collet chuck assembly has a mount with a front portion and a rear portion adapted to be connected to the spindle. The mount has an axial opening extending therethrough. An axially-extendable collet closing sleeve is disposed within the axial opening of the mount, the collet closing sleeve having a first cam surface. The collet chuck assembly also includes a radially-expandable collet head, which has a second cam surface that engages the first cam surface, and at least one lip having a third surface. The collet chuck assembly also has a cap that mounts to the front portion of the mount and engages the collet head to prevent the collet head from moving axially-forwardly. The cap has at least one tab with a fourth surface that engages the third surface of the lip of the collet head to prevent the collet head from moving axially-rearwardly. The fourth surface of the at least one tab and the third surface of the at least one lip are disposed axially forward from a forward portion of the sleeve.
A further aspect of the present invention provides a collet chuck assembly that has a mount with a front portion and a rear portion adapted to be connected to a spindle. The mount has an axial opening extending therethrough. A collet head is disposed radially-inwardly from the collet closing sleeve, the collet head defining an inner order hole. A cap mounts to the front portion of the mount and has a radially-extending slinger bore that opens into a space between the collet head and the mount. The slinger bore is adapted to direct debris outwardly out of the space between the mount and the collet head.
Additional and/or alternative objects, features, and advantages of the present invention will become apparent from the following description, the accompanying drawings, and the appended claims.